(Solved): 7.- Acid rain from the burning of fossil fuels has caused many of the lakes around the world to be ...

7.- Acid rain from the burning of fossil fuels has caused many of the lakes around the world to become acidic. The biology in these lakes often collapses because of the rapid and unfavorable changes in water chemistry. A lake is classified as nonacidic if it has a pH greater than 6. Researchers measured the \( \mathrm{pH} \) of high mountain lakes in the Southern Alps. These data are approximately normal. The \( \mathrm{pH} \) levels for 15 lakes is presented in the list below. At the \( 1 \% \) significance level, do the data provide sufficient evidence to conclude \( \begin{array}{lllllll}6.3 & 6.5 & 5.7 & 6.9 & 6.7 & 7.9 & 5.8\end{array} \) For these data \( \bar{x}=6.6 \) and \( s=0.672 \) To answer this question provide the following elements to perform the hypothesis test: a) Define \( \mathrm{H}_{0} \) : mean \( =6 \) b) Define \( \mathrm{H}_{\mathrm{a}} \) : mean \( >6 \) c) You will use (circle your answer): the \( z \) statistic the \( t \) statistic d) Given that \( \alpha=0.01 \), define the critical value(s): e) The Rejection Region for this test is: f) The observed value of the test statistic is: g) Your conclusion is (circle your answer): these lakes are not acidic these lakes are acidic h) The p-value for this test is: \( \quad \) so you: \( \quad \) Keep \( \mathrm{H}_{0} \quad \) Reject \( \mathrm{H}_{0} \)